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Renewable Energy Glossary

Geothermal Energy

Energy produced by the internal heat of the earth; geothermal heat sources include hydrothermal convective systems; pressurized water reservoirs; hot, dry rocks; manual gradients; and magma. Geothermal energy can be used directly for heating or to produce electric power.

Geothermal Heat Pump

A type of heat pump that uses the ground, ground water, or ponds as a heat source and heat sink, rather than outside air.

GFPD

Ground fault protection device (GFPD) is a device that detects whether fault current is being carried by the equipment-grounding conductors and can disable the system.

Gin Pole

Either of two different types of devices used with wind generator towers. With a tilt-up tower, it describes the lever that helps tilt the tower up. With a fixed tower, it describes a temporary crane used to raise tower sections or the wind generator.

Glazing

The glass layer of windows and doors that transmits light.

Glycol

An antifreeze, heat transfer fluid that is circulated through closed loop solar hot water collectors.

Governing

Limiting the output and speed of a wind generator. In respect to small wind generators, governing typically is accomplished via furling, pitch control, or stall.

Gravity Head

The atmospheric resistance that a pump must overcome to raise a fluid above its level at rest.

Grid-Connected System

A PV system that is tied to the utility grid, including both grid-direct and grid-tied with battery back-up systems.

Grid-Direct System

A PV system that can sell electricity to the utility grid. These systems do not have energy storage and are required to shut down if the utility is not present, such as during a blackout.

Grid-Direct Systems

PV systems that can sell electricity to the utility grid. These systems do not have energy storage and are required to shut down if the utility is not present, such as during a blackout.

Grid-Tied with Battery Backup System

A PV system that is connected to the utility, and can sell excess energy back to the grid. Because these systems have batteries, some specified backed-up loads can be powered during a utility outage.

Ground

Ground means the earth.

Ground Fault

An unintentional, electrically conducting connection between a current-carrying conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.

Ground Fault Protection Device

A device that detects whether fault current is being carried by the equipment-grounding conductors and can disable the system.

Ground Mounts

PV racking structures affixed to the ground via concrete piers, metal or wood piles, or other attachments or ballast that provide support and stability.

Grounded

To be intentionally connected to earth through a ground connection, at a reference point of zero volts or zero potential.

Grounded Conductor

A current-carrying conductor that is intentionally connected to earth ground at one point to create a zero-voltage reference.

Grounding Electrode

A conducting object, often a rod, ring, or plate, establishing a direct connection to earth.

Grounding Electrode Conductor

The conductor used to connect the grounding electrode or grounding electrode system to the system grounded conductor, to the equipment, or to both.

Guy Wires

Steel cables that support a tower. Tilt-up towers have four sets of guy wires, and therefore four guy anchors. Fixed-guyed towers have three sets of guy wires and three anchors.